1. Field of the Invention
The subject invention relates to a method and apparatus for ablating anatomical organs, lumens or other tissue and more particularly to a protective cover that isolates the tissue to be ablated from surrounding tissue to permit complete and rapid ablation, or other manipulation, of the tissue without damaging surrounding tissue.
2. Description of the Related Art
Anatomical organs, such as the uterus, gall bladder, large intestine, and the like, can develop abnormal conditions, such as excessive bleeding. It is known to treat such abnormal organ conditions by removal of a portion or an entirety of the organ. However, removal of an organ ordinarily requires invasive surgery and general anesthesia and thus is expensive and presents a relatively high risk to the patient. Also, removal of an organ eliminates the function of the organ entirely. This may require additional treatment to replace the organ function. Further, removal of an organ can be psychologically traumatic to the patient, particularly in the case of reproductive organs.
It is also known to ablate tissue by heating the tissue (thermal ablation), freezing the tissue (cryogenic ablation), mechanically cutting or scraping the tissue, or otherwise applying energy or manipulation of the tissue. The terms "ablating" and "ablation" as used herein broadly refer to killing, removing, or otherwise destroying or altering tissue or the function of tissue, such as through cauterization, coagulation, sclerosing, necrosing, removal or the like. Ablation is accomplished by introducing an ablating member to an area proximate the damaged tissue. Thermal ablating members can include a laser, an RF electrode, a radiation member, an electrically resistive coil, a scraping device, or any other method of delivering energy. Lasers are inherently focused to a small area and thus laser ablation requires that the surgeon direct the laser at the particular tissue to be ablated and, if the area to be ablated is large, the surgeon must move the laser to cover the entire area as if painting the area. Also, if the laser energy is too high, or the surgeon lingers too long on one area, the laser energy can cause the tissue to be cut, perforated, or overheated and other organs can be damaged. Similarly, other thermal and cryogenic devices must be carefully applied and controlled to insure that the abnormal tissue is affected without damaging other normal tissue or organs that are proximate the damaged tissue . Therefore, known ablation techniques use endoscopes or the like to inspect the condition of the tissue and complex controls to control the application of energy to the damaged tissue.
For example, a diseased condition of the uterus, known as endometriosis, is often treated by ablating the diseased tissue, i.e. the inner layer of the uterus known as the endometrium. Of course, it is desirable to cause necrosis in the endometrium without damaging other surrounding organs. Since other organs, such as the bladder, are closely pressed against the uterus, it is quite difficult to avoid damage to other organs. Thus, conventionally, the endometrium had to be ablated, by applying heat for example, without heating the outer layer of the uterus known as the myometrium. Therefore, known ablating techniques for treating the uterus have applied energy in relatively low levels for a precisely controlled period of time. For example, the tissue is heated to about 200.degree. F. (in the case of thermal ablation) or cooled to below 32.degree. F. (in the case of cryogenic ablation) for several minutes. This often fails to induce necrosis in the entire endometrial layer because the inner surface of the uterus is not smooth and has many crevices, for example areas proximate the fallopian tubes, to which it is difficult to apply energy and the thickness of the endometrium often varies. Also, higher levels of heating or cooling can damage surrounding organs if applied for too long and thus precise time and temperature control is required. Also, a procedure known as "dilation and curretage" (D and C) is often used to treat endometriosis or other uteran abnormalities. The, D and C procedure requires mechanical scraping. If the scraping is not carefully controlled, the myometrium can be damaged and even perforated, in which case surrounding organs can be damaged. Also, it is difficult to ensure that all of the diseased tissue is removed.
U.S. Pat. No. 3,645,265 discloses a spring member that is inserted into the uterus and then expanded to press against the uterine wall. The spring is then used as a cautery electrode to cause necrosis. However, heating is intensified at portions of the uterine wall that contact the spring and thus localized higher degrees of ablating may occur. In order to cause necrosis in large areas of the uterus, such as in the entire endometrium, it may be necessary to apply excessive heat to areas which contact the spring. This can damage surrounding tissue.
U.S. Pat. No. 5,105,808 discloses an applicator having a distendable bladder that is inserted into the uterus. A heated fluid is introduced into the bladder to cause necrosis of the uterus. However, the bladder may not contact all of the crevices of the uterine wall and thus incomplete necrosis or undesired tissue damage may occur. U.S. Pat. No. 5,449,380 attempts to solve this problem by providing spring members in an inflatable bladder that cause the bladder to conform more closely to a standard shape of a uterus. However, since each uterus is shaped differently, even the device disclosed in U.S. Pat. No. 5,449,380 may fail to reliably contact all portions of the endometrium and thus may exhibit the limitations noted above.
U.S. Pat. No. 5,242,390 discloses the introduction of heated liquid onto the uterus for ablation. U.S. Pat. No. 5,242,390 also discloses that silicone polymer rings or physiologic saline solution can be disposed internally in the uterus to protect the fallopian tubes from damage due to the applied heat. However, these patents also fail to disclose any protection for other surrounding organs.
U.S. Pat. No. 5,575,788 discloses an ablating apparatus having an expandable porous member. Electrolytic solution is released through the porous member and an electrically conductive conforming member acts as an ablating electrode. The porosity of the porous member varies to concentrate the electrolytic solution at desired areas. U.S. Pat. Nos. 5,277,201, 5,443,470, and 5,433,708 disclose limiting temperature to prevent damage to normal tissue. However, no adequate solution exists for preventing damage to surrounding organs while completely ablating a damaged organ. Accordingly, conventional uterine ablating techniques are not reliable and must be repeated several times in many patients to be effective. Therefore, most uterine problems are addressed by removing the uterus. This can cause physical and psychological trauma. Often this trauma can inhibit the body's immune system and ability to generate anticancer agents or the like.
Uterine ablating is ordinarily accomplished by a device that is inserted vaginally. However, it is well known to accomplish ablation of other organs using endoscopic or other minimally invasive devices that are inserted through a portal sleeve disposed in an aperture formed in the patient's skin by an obturator, such as a trocar.
Finally, the potential for error in known procedures makes it necessary for the procedures to be carried out by a physician in a surgical environment. This increases the cost of the procedures.